A device for determining the direction of incidence of optical radiation which uses a photodiode unit consisting of a linear array of photodiodes contained in a light-tight box is disclosed, for example, in DE-OS published German patent application No. 29 31 818. The wall of the box opposite the the photodiode unit contains a slit extending transversely to the photodiode array or a suitable lens by which radiation incident within a predetermined angular range is focused onto an area of the photodiode unit corresponding to the angle of incidence. A subsequent circuit evaluates the signals delivered by the photodiodes. The problems caused by large differences in radiation intensity, crosstalk between adjacent photodiodes, and parasitic radiation are not dealt with.